Throughout this application various publications are referenced by arabic numerals with parentheses. Full citations for these references may be found at the end of the specification immediately preceding the claims. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of art as known to those skilled therein as of the date of the invention described and claimed herein.
This invention concerns the heavy metal salts of hyaluronic acid.
Hyaluronic acid is present in various connective tissues of animals, such as skin and cartilage. Some organs are specifically rich in hyaluronic acid, such as the umbilical cord, synovial fluid, the vitreous humor and rooster combs. In addition, hyaluronic acid is produced by various microorganisms, such as streptococci Type A and C.
In skin and cartilage, the role of hyaluronic acid is to bind water and retain the tonicity and elasticity of the tissue. In joint fluids, the viscous hyaluronic acid solution serves as a lubricant to provide protective environment to the cells. A solution of ultrapure hyaluronic acid from rooster combs has been in use for several years as a supportive medium in ophthalmic surgery, see U.S. Pat. No. 4,141,973 of E. A. Balazs (1979). A similar preparation has been shown to be beneficial in the treatment of inflamed knee joints of race horses. Another use of hyaluronic acid results from its highly hydrophilic nature, making it an ideal constituent of moisturization lotions for cosmetic use, U.S. Pat. No. 4,303,676 of E. Balazs (1981).
Hyaluronic acid has been isolated from the various biological sources, as described above, including microbial broth. The isolation and characterization of hyaluronic acid has been described by Meyer et al., J. Biol. Chem. 107,629 (1934); J. Biol. Chem. 114,689 (1936), and has recently been reviewed in Methods in Enzymol. 28, 73 (1972). The structure of hyaluronic acid was elucidated by Weissman et al., J. Am. Chem. Soc. 76, 1753 (1954) and Meyer, Fed. Proc. 17, 1075 (1958). Other publications such as, U.S. Pat. No. 4,141,973, Feb. 27, 1979 by E. A. Balazs, concerned the production and purification of hyaluronic acid from the sources such as animal connective tissue.
Radioactively labelled hyaluronic acid and sodium salt thereof has been produced by growing streptococcus in fermentation broth containing radioactively labelled glucose. (3)
Numerous silver compounds having a wide range of uses are known. These include silver acetate and silver chlorate which may be used as oxidizing agents; silver bromide and silver oxalate which are used in photography; silver difluoride for use in the flourination of hydrocarbons; silver chloride and silver cyanide for use in silver plating; and silver chromate (VI) and silver oxide which may be employed as catalysts, to name just a few.
The silver ion has also been shown to be an effective antimicrobial agent. It is not associated with significant side effects, is not an allergen, and is only rarely associated with the induction of resistant strains of bacteria. Many silver salts are useful as topical anti-infectives or as antiseptics. These include: silver fluoride, silver iodide, silver lactate, mild silver protein and silver nitrate. Silver lactate and silver nitrate may also be employed as astringents and silver picrate and silver sulfadiazine may be used as antimicrobial or antibacterial agents.
It is believed that silver compounds produce their antimicrobial effects by the time-dependent release of silver ions and their effectiveness is direclty related to the constant presence of the free ions in the tissues. The use of simple silver salts, such as silver nitrate, as an antibacterial agent has been limited by the requirement of frequent applications to achieve effective concentrations of the silver ions (10-20 .mu.g/ml).
Although the use of silver sulfadiazine, a more complex silver compound, results in a more sustained release of the silver metal ions, the use of both silver nitrate and silver sulfadiazine is often accompanied by adverse side-effects due to the anion part of the salts, namely nitrate and sulfadiazine. For example, sulfadiazine has such side effects as leucopenia and immunosuppression activity. Other silver preparations, such as foils and silver nylon, have recently been offered for use, but their release of silver ions is limited and do not result in high enough concentrations.
Thus, the need for a silver compound providing sustained release of the silver metal ion, but having no adverse side effects is apparent.
Rheumatoid arthritis is characterized by severe inflammation of the joints which is followed by the appearance of degraded hyaluronic acid in the joint fluid. In severe cases, anti-inflammatory agents such as corticosteroids and gold salts, e.g. gold sodium thiomalate or gold sodium thiosulfate are administered intra-articularly. However these agents are active for only a short duration, and there is a need to sustain their action. Thus, the invention of an anti-inflammatory agent having sustained action would meet a long felt need and be a significant advance in the anti-inflammatory art.
The present invention is directed to heavy metal salts of hyaluronic acid, including silver hyaluronate, gold hyaluronate, cerium hyaluronate, and tungsten hyaluronate.
The invention is also directed to methods of inhibiting microbial growth utilizing these heavy metal salts.
The present invention concerns methods of producing silver hyaluronate, compositions containing silver hyaluronate, and the treatment of wounds, burns and infections, especially soft-tissue infections and gonoccocal opthalmalogical infections, with silver hyaluronate.
The invention also concerns treating arthritis and joint inflammation with gold hyaluronate.
Finally, this invention is directed to compositions containing radioactively labelled heavy metal salts e.g. .sup.14 C AgHA, which compositions may be used for diagnostic purposes.